package com.lagou.sqlSession;

import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;
import org.apache.log4j.net.SyslogAppender;

import javax.lang.model.type.TypeVariable;
import java.lang.reflect.*;
import java.util.List;

public class DefaultSqlSession implements SqlSession {

    private Configuration configuration;

    public DefaultSqlSession(Configuration configuration) {
        this.configuration = configuration;
    }

    @Override
    public <E> List<E> selectList(String statementId, Object... params) throws Exception {
        //将要完成对simpleExcutor里面的query调用
        SimpleExcutor simpleExcutor = new SimpleExcutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
        List<Object> list = simpleExcutor.query(configuration, mappedStatement,params);
        return (List<E>) list;
    }

    @Override
    public <T> T selectOne(String statementId, Object... params) throws Exception {
        List<Object> objects = selectList(statementId, params);
        if (objects.size()==1){
            return (T) objects.get(0);
        }else {
            throw new RuntimeException("查询结果为空或者返回结果过多");
        }
    }

    @Override
    public Integer updateOne(String statementId, Object... params) throws Exception {
        try {
            //将要完成对simpleExcutor里面的update调用
            SimpleExcutor simpleExcutor = new SimpleExcutor();
            MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
            Integer res = simpleExcutor.update(configuration, mappedStatement,params);
            return res;
        } catch (Exception e){
            System.out.println(e.getMessage());
            return 0;
        }
    }

    @Override
    public <T> T getMapper(Class<?> mapperClass) {
        //使用JDK动态代理来为Dao接口生成代理对象，并返回
        Object proxyInstance = Proxy.newProxyInstance(DefaultSqlSession.class.getClassLoader(), new Class[]{mapperClass}, new InvocationHandler() {
            @Override
            public Object invoke(Object o, Method method, Object[] args) throws Throwable {
                // 底层都还是去执行JDBC代码 //根据不同情况，来调用selctList或者selectOne
                // 准备参数 1：statmentid :sql语句的唯一标识：namespace.id= 接口全限定名.方法名
                // 方法名：findAll

                String sqlType = "";
                String methodName = method.getName();

                String className = method.getDeclaringClass().getName();

                String statementId = className+"."+methodName;

                // 准备参数2：params:args
                // 获取被调用方法的返回值类型
                Type genericReturnType = method.getGenericReturnType();
                // 判断是否进行了 泛型类型参数化
                if(genericReturnType instanceof ParameterizedType){
                    List<Object> objects = selectList(statementId, args);
                    return objects;
                }else if (method.getReturnType().equals(Integer.class) ){   // 判断返回类型是否为Integer基本类型，是的话执行update方法
                    return updateOne(statementId,args);
                }else {
                    return selectOne(statementId,args);
                }

            }
        });
        return (T) proxyInstance;
    }
}
